You got this the wrong way; Kierkegaard sees modern society as causing inauthenticity - this is not about anti-social language, normies or anything at all like that, this is an existential 'analysis' of the human condition after/during the start of the industrial era.Suddenly we all use labels for everything, your identity is an item you take off the shelfs of some supermarket. It didn't use to be like that, actually we haven't had a way of living like that likely ever in human history.

So did the 'authentic' medieval peasant just browse instagram all day and consider himself a special singular authentic individual because it pleased his ego? Likely not. His identity was just formed under very different circumstances than how our identities are formed today. And the way today forces an 'inauthentic' formation of said identity. That is what Kierkegaards beef is with modern mass society.

**EDIT
A quote by Kierkegaard in relation to the inauthenticity of identity caused by the press. I feel we all can relate to what he means, especially cause of the times we live in.

"More and more people renounce the quiet and modest tasks of life, that are so important and pleasing to God, in order to achieve something greater; in order to think over the relationships of life in a higher relationship till in the end the whole generation has become a representation, who represent…it is difficult to say who; and who think about these relationships…for whose sake it is not easy to discover. The real moment in time and the real situation being simultaneous with real people, each of whom is something; that is what helps to sustain the individual. But the existence of a public produces neither a situation nor simultaneity. The individual reader of the Press is not the public, and even though little by little a number of individuals or even all of them should read it, the simultaneity is lacking. Years might be spent gathering the public together, and still it would not be there. This abstraction, which the individuals so illogically form, quite rightly repulses the individual instead of coming to his help. The man who has no opinion of an event at the actual moment accepts the opinion of the majority, or, if he is quarrelsome, of the minority. But it must be remembered that both majority and minority are real people, and that is why the individual is assisted by adhering to them. A public, on the contrary, is an abstraction"